Self-consistent absorption correction for quantifying very noisy X-ray maps: group III nitride nanowires as an...

Area of Science:

• Materials Science
• Analytical Chemistry
• Electron Microscopy

Background:

• Energy-dispersive X-ray (EDX) mapping visualizes elemental distribution in samples using scanning transmission electron microscopy.
• Accurate quantification in EDX mapping requires precise background elimination and correction for X-ray self-absorption and fluorescence.
• These corrections are especially critical for thicker, rougher samples, low X-ray take-off angles, and low-energy X-ray lines.

Purpose of the Study:

• To adapt and validate a self-consistent absorption correction method for EDX mapping of InGaN and AlGaN layers within GaN nanowires.
• To address the challenges posed by extremely noisy elemental maps with very low signal intensities (few counts per pixel).
• To demonstrate the necessity of sub-pixel accuracy in background correction for reliable quantification of such noisy data.

Main Methods:

• Application of a self-consistent absorption correction method based on effective k*-factors.
• Utilizing simulated curves of K/L line intensity ratios for automatic selection of correction factors.
• Implementing sub-pixel accuracy for background intensity correction, including interpolation of maps from neighboring X-ray lines.

Main Results:

• The self-consistent absorption correction method proved effective even for extremely noisy EDX maps where elemental layers are barely visible.
• Accurate quantification was achieved for InGaN and AlGaN layers in GaN nanowires (66-375 nm thick).
• Critical importance of accurate background estimation, particularly for Ga L-line intensity, was highlighted.

Conclusions:

• The developed self-consistent absorption correction method is robust for analyzing noisy EDX elemental maps.
• Precise background estimation is essential for reliable quantification in challenging nanoscale material analysis.
• This approach enhances the capability of EDX mapping for complex semiconductor nanostructures.